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.Dd August 25, 2021
.Dt VOP_DEALLOCATE 9
.Os
.Sh NAME
.Nm VOP_DEALLOCATE
.Nd zero and/or deallocate storage from a file
.Sh SYNOPSIS
.In sys/param.h
.In sys/vnode.h
.Ft int
.Fo VOP_DEALLOCATE
.Fa "struct vnode *vp"
.Fa "off_t *offset"
.Fa "off_t *len"
.Fa "int flags"
.Fa "int ioflag"
.Fa "struct ucred *cred"
.Fc
.Sh DESCRIPTION
This VOP call zeroes/deallocates storage for an offset range in a file.
It is used to implement the
.Xr fspacectl 2
system call.
.Pp
Its arguments are:
.Bl -tag -width offset
.It Fa vp
The vnode of the file.
.It Fa offset
The start of the range to deallocate storage in the file.
.It Fa len
The length of the range to deallocate storage in the file.
.It Fa flags
The flags of this call.
This should be set to 0 for now.
.It Fa ioflag
Directives and hints to be given to the file system.
.It Fa cred
The credentials of the caller.
.El
.Pp
.Fa *offset
and
.Fa *len
are updated to reflect the portion of the range that
still needs to be zeroed/deallocated on return.
Partial result is considered a successful operation.
For a non-partial successful completion,
.Fa *len
is updated to be the value 0, and
.Fa *offset
is incremented by the number of bytes zeroed before the end-of-file.
.Sh LOCKS
The vnode should be locked on entry and will still be locked on exit.
.Sh RETURN VALUES
Zero is returned if the call is successful, otherwise an appropriate
error code is returned.
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er EINVAL
Invalid
.Fa offset , len
or
.Fa flags
parameters are passed into this VOP call.
.It Bq Er ENODEV
The vnode type is not supported by this VOP call.
.It Bq Er ENOSPC
The file system is full.
.It Bq Er EPERM
An append-only flag is set on the file, but the caller is attempting to
zero before the current end of file.
.El
.Sh SEE ALSO
.Xr vnode 9
.Sh AUTHORS
.Nm
and this manual page was written by
.An Ka Ho Ng Aq Mt khng@FreeBSD.org
under sponsorship from the FreeBSD Foundation.
